1,136 research outputs found
Laparoscopy uptake for paediatric appendicectomy: a comparison of general surgeons versus specialist paediatric surgeons in England from 1997 to 2015
No full textIntroduction: laparoscopy is used in as many as 95% of adult appendicectomies. There is level I evidence showing that it reduces wound infection, postoperative ileus and length of inpatient stay in children compared with the open approach. The aim of this study was to report the uptake of laparoscopy for paediatric appendicectomy in England and to determine whether this was similar for general surgeons (GS) and specialist paediatric surgeons (SPS). Methods: Hospital Episode Statistics data were obtained for all children aged <16 years who had an OPCS 4.6 code for emergency appendicectomy from 1997 to 2015 (18 years). Data are analysed to compare rate of laparoscopic vs open procedures for GS and SPS over time and to investigate factors associated with the use of laparoscopy. Results: there were 196,987 appendicectomies and where specialty was available, 133,709 (79%) cases were undertaken by GS and 35,141 (21%) by SPS. The rate of cases undertaken with laparoscopy for both specialties combined increased from 0.8% in 1998 to 50% in 2014 (p<0.0001). In 2014, this rate was 41% for GS compared with 71% for SPS (p<0.0001). Female gender (odds ratio (OR)=1.84, 95% confidence interval (CI) 1.80-1.90), increasing age (OR=1.18, 95% CI 1.18-1.19 per year) and treatment by SPS (OR=3.71, 95% CI 3.60-3.82) were all factors positively associated with use of laparoscopy in multivariate analysis. Conclusions: there has been a vast increase in the proportion of appendicectomies undertaken laparoscopically in children. Despite adjusting for patient factors, laparoscopy was used significantly less by GS when compared with SPS. This difference is most apparent in younger children.</p
Numerical simulation of free surface flows with steep gradients
No full textCivil Engineering and Geoscience
Finite element modelling of transport and non-hydrostatic flow in environmental fluid mechanics
No full textSectie VloeistofmechanicaCivil Engineering and Geoscience
Evolution of the floc size distribution of cohesive sediments
No full textThis thesis focuses on the flocculation process of cohesive sediment (mud) and in particular on the time evolution of the floc size distribution. Mud is mainly observed in estuarine environment and its settling velocity is strongly affected by its floc size distribution. Small flocs (1-50 micrometers) have a very small settling velocity and tend to remain in suspension while large flocs (50 micrometers-centimeters) are characterized by a large settling velocity and deposit rapidly inducing bed siltation. Moreover, small suspended flocs reduce light transmission through the water column and may carry pollutants through large distances. The investigation of the evolution of the floc size distribution is therefore relevant in the fields of civil engineering and ecology. Flocculation is the combination of the processes of aggregation and breakup and is influenced by the sediment and water properties, sediment concentration and turbulent motion. The relation between small scale particle-particles interactions and large-scale flocculation behavior is investigated in this thesis through both experimental and modeling work. In particular a series of coupled experiments where both the surface charge of the particles, quantified by their zeta-potential, and the flocculation behavior are observed. Flocculation is then modeled by means of a population balance equation where flocs are distributed in size classes and aggregation and breakup represent respectively birth and death of flocs in each class.Environmental fluid mechanicsCivil Engineering and Geoscience
Hydrodynamic models in urban drainage application and calibration
No full textCivil Engineering and Geoscience
Deterministic and Stochastic Modelling of Ocean Surface Waves
No full textPredicting the mean wave statistics in the nearshore, for instance the significant wave height, has predominantly been the domain of operational stochastic wave models based on the radiative transport (or energy balance) equation. Although reasonably successful in the nearshore, these models were originally developed for oceanic scales, and necessarily neglect or parametrise processes that are only significant in shallow water, such as the linear processes of interference and diffraction, or the nonlinear triad wave-wave interactions and dissipation due to wave breaking. In this dissertation we investigate the possibility of predicting the wave statistics on small scales in strongly non-linear conditions, such as found in the surfzone, using the recently developed Surface WAves till SHore (SWASH) model, whereas on larger scales we pursue a generalisation of existing stochastic models by incorporating coherent effects, hereby extending these models to include interference and diffractive effects.Hydraulic EngineeringCivil Engineering and Geoscience
Particle models for transport in three-dimensional shallow water flow
No full textCivil Engineering and Geoscience
Harnessing high altitude solar power
No full textAs an intermediate solution between Glaser's satellite solar power (SSP) and ground-based photovoltaic (PV) panels, this paper examines the collection of solar energy using a high-altitude aerostatic platform. A procedure to calculate the irradiance in the medium/high troposphere, based on experimental data, is described. The results show that here a PV system could collect about four to six times the energy collected by a typical U.K.-based ground installation, and between one-third and half of the total energy the same system would collect if supported by a geostationary satellite (SSP). The concept of the aerostat for solar power generation is then briefly described together with the equations that link its main engineering parameters/variables. A preliminary sizing of a facility stationed at 6 km altitude and its costing, based on realistic values of the input engineering parameters, is then presented
10 Questions to.. Professor Guus Stelling about 3Di water management
No full textSince January 2002 Prof. Stelling is professor of fluid mechanics in the Civil Engineering and Geosciences faculty of the Technical University in Delft. Until July 2010 he was the head of the environmental fluid mechanics section. Presently professor Stelling is also visiting professor at the National University of Singapore in the Faculty of Engineering. In addition he is senior advisor at Deltares. InterviewHydraulic EngineeringCivil Engineering and Geoscience
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